...It will track where you go and show you the way back
Oh, yeah, I fergot. Though the eTrex and the Rino can't do automatic routing ("take me from x to y") but they store the route you've traveled -- like a trail of breadcrumbs -- so if you're on a country "get lost" ride, not only will it show you the streets and towns you're near, but all you have to do once you're done is turn around and backtrack home.
The R.A.M. mounting system uses a rubber ball, btw, and it supresses vibration nicely. My etrex is very readable at speed. They have a cradle for the Rino, as well as probably all other Garmin models.
Just to give you an idea of what these units are capable of: Mine has 32mb of memory. With that, I have street-level maps of all of MD, VA, WV, a third of PA, and a small part of NY (NYC, LI, etc.) and CT. I'm sure the 60CS w/50-odd mb of ram, for example, could hold street level maps for a long trip. All of these have a "base map" with lots of cities and all of the interstates (and some other major roads) in NA.